( Reaffirmed 2001 ) Is:9447~1980 Indian Standard GUIDELINES FOR ASSESSMENT OF SEEPAGE LOSSES FROM CANALS BY ANALYTICAL METHOD Canals and Canal Linings Sectional Committee, BDC 57 Chairman Representing Chukha Hyde1 Project, Bhutan SHRI S. B. KHARE Members Irrigation and Research Institute, Khagaul ( Patna ) Department, Government of Irrigation ADMINISTRATOR Maharashtra, Bombay Central Ground Water Board, Chandigarh SHRI N. C. BHATNAQAR Snax CHICKARMANE Union Carbide India Ltd, Bombay SWRI S. K. KARAMCHANDANI ( Altarnate ) Irrigation and Power Department, Government of CHIEF ENGINEER Andhra Pradesh, Hyderabad DR J. PU~USHOTHAM ( Alternate ) Irrigation Works, Government of Punjab, C HIEF ENGINEER ( C ) Chandigarh D IRECTOR CENTRAL DESIGNS ( Alternate) Public Works Department, Government of Tamil C HIEF ENC~NEER ( IRRIGATION ) Nadu, Madras S R D Y C HIEF E NGINEER ( IRRIGATION ) ( Alternate ) C HIEF E NGINEER ( I R R I G A T I o N ) Public Works Department, Government of ( SOUTH) Karnataka, Bangalore SHRI 0. P. DATTA D R R. J. GARDE ADDITIONAL D IRECTOR CHIEFENGINEER( TUNGABHADRA PROJECT) (Altevzatc) D R A. S. C WAWLA (Alternate) Beas Designs Organization, Nangal Township Water Resources Development Training Centre, University of Roorkee, Roorkee ( UP) Irrigation Department, Government of Rajasthan, laipur _ Central Water Commission, New Delhi DIRECTOR D IRECTOR ( B & CD-I ) D EPUTY D IRECTOR ( B & CD-I ) (Alternate ) D IRECTOR ( B & CD-II ) Central Water Commission, New Delhi D EPUTY D IRECTOR ( B & CD-II j ( Alternate ) ( Continued on page 2 ) @ Copyright 1980 INDIAN STANDARDS INSTITUTION This publication is protected under the Indian Copyright Acf (XIV of 1957) and reproduction in whole or in part by any means except with written permission of the publisher shall be deemed to be an infringement of copyright under the said Act. IS : 9447 - 1980 ( Continuedfiom page SHRI 1) Representiq Planning Commission, Government of India, New Delhi Concrete Association of India, Bombay Irrigation Department, Government of Uttar Pradesh, Lucknow Members K. M. M AHESHWARI S HRI E. T. ANTIA (Alfernate ) SHRI GAURI KANTA MISRA SHRI SHRI Y. S HRI N. K. D IKSHIT ( Alternate ) K . MEHTA SHRI P. C. S AXENA SHR~ V . P. BHATT ( Alternate ) S ECRETARY SHRI M. K. SINCHAL S HRI JAGDISH MOI~AN ( Alterndc) S HRI K. T. SUBUDHI S HRI R. K. AQOARWAL ( Ahnate) Fibreglass Pilkington Ltd, Bombay G. H. RODRICKS SHRI E. SU B R A M A N I A N ( Ahrnate ) Central Water and Power Research Station, Punt Central Board of Irrigation and Power, New Delhi Irrigation Research Institute, Roorkee Irrigation and Power Department, Government of Orissa, Bhubaneshwar Irrigation and Power Department, Government of SUPERINTENDINOENGINEER Haryana, Chandigarh ( PROJECT & DESIGN C IRCLE ) SUPERINTENDING E NGINEER (S. Y. L . D ESIGN C IRCLE ) ( Alternnfe ) Director General, IS1 ( Ex-ofjcio Member ) S HRI D. AJITHA SIMHA, Director ( Civ Engg ) secretary SHRI V. KALYANASUNDARAY Assistant Director ( Civ Engg), IS1 2 IS : 9447 6 1980 Indian Standard GUIDELINES FOR ASSESSMENT OF SEEPAGE LOSSES FROM CANALS BY ANALYTICAL METHOD 0. FOREWORD 0.1 This Indian Standard was adopted by the Indian Standards Institution on 29 February 1980, after the draft finalized by the Canals and Canal Linings Sectional Committee had been approved by the Civil Engineering Division Council. 0.2 Irrigation project design, operation and maintenance, and canal lining research and development, require accurate and economical measurement of seepage rates. The possible benefits from canal lining are saving in water, elimination of waterlogging, and reduction in maintenance cost. Hence, correct assessment of seepage losses from unlined canals is very important for evaluation of benefits from lining and field observations. 0.3 The loss of water by seepage from unlined canals in India generally varies from 0.3 to 7.0 m3/s/106 m2 depending on the permeability of soil through which the canal passes, location of water table, distance of drainage, bed width, side slope and water depth inside the canal. In addition, flow velocity, soil, water temperature, atmospheric pressure and stratification of the underlying soil also affect the seepage rate. 0.4 The seepage losses from unlined canals can be calculated by analytical methods or determined by direct measurements on the channels. The analytical calculations of seepage losses based on coefficient of hydraulic conductivity of soil and the boundary conditions of the flow system, are of particular value for the canals which are in the planning stage. The method of direct measurement of seepage losses are applicable to the existing canals. 0.5 Currently, accepted methods for direct measurement of seepage losses from existing canals are the ponding and inflow-outflow. In addition, there are special methods such as tracer technique, seepage meter, electrical logging or resistivity measurement, and piezometric surveys. The ponding and inflow-outflow methods are applicable regardless of canal or soil conditions. The seepage meter cannot be used where the channel has rocky bottom or heavy weed growth. The tracer technique is best suited to canals in homogeneous and isotropic formations. 3 IS -: 9447 - 1980 0.6 Valuable assistance has been rendered by Dr A. S. Chawla, Professor, Water Resources Development Training Centre, Roorkee, in the preparation of this standard. 0.7 In the formulation of this standard, due weightage has been given to international co-ordination among standards and practices prevailing in different countries in addition to relating it to the practices in the field in this country. This has been met by deriving considerable assistance from the following publications: G ARG, SATYA P., and C HAWLA, A. S. Seepage from Trapezoidal Channels. Journal of the Hydraulics Division, AXE, Vol 96, No. HY6, Proc. Paper 7335, June 1970, pp. 1261-1282. SHARMA, H. D. and C HAWLA , A. S. Canal Seepage with Boundary at Finite Depth. Journal of the Hydraulics Division, ASCE, Vol 105, No. HY7, July 1979. V EDERNIKOV , V. V. Seepage from Triangular and Trapezoidal Channels. Machine Zapiski, Moskovskogo Institua Inzhenerov Vodnogo Khozyaistva No. 2, pp. 248-288, 1936. 1. SCOPE 1.1 This standard deals with assessment of seepage losses in open channels by analytical method. 1.2 This standard is applicable in open channels along water shed which are not normally subject to recharge from the ground water. 2. NOTATIONS The following symbols are used in this standard: B - width of channel bottom in z-plane ( metres ) B, = width of channeI water surface in z-plane ( metres ) b = width of channel bottom in &plane ( metres) H = water depth of channel ( metres ) 11 - drop between channel and drain water levels ( metres ) k = coefficient of permeability ( metres/sec ) L = ~drainage distance from water line of the channel ( metres ) (I = volume rate of seepage per unit length of channel (cubic metres/ set/m ) T = depth of pervious medium from drain bed ( metres) XK = canal side slope angle with horizontal in z-plane ( radians ) XU' = canal side slope angle with horizontal in &plane ( radians ) 4 IS :9447-1980 u, p, y = transformation parameters (dimensionless) 0= Ol+i(l: 'complexvariable representing Zhukovsky's function d = potential function 3. ANALYTICAL METHOD 3A The -seepage 10SWS from unlined canals depend on the canal dimension, the permeability of the subsoil, distance of governing drainages and the difference in the water levels of canal and the drainage. Initial seepage losses are high due to steep gradient, but as the subsod becomes saturated the gradients flatten and ultimately stabilize. 3.2 Analytical solutions are available for evaluating seepage losses from canals under steady conditions for the following cases. The solutions given here are for homogeneous and isotropic medium. The flow is assumed to @ laminar and hence follows Darcy's law. a) Canals located in medium extending up to inffnite depth with shallow water table; b) Canals located in medium extending up to finite depth with shallow water table; and c) Canals located in medium extending up to infinite depth with deep water table. 3.3 The seepage from canal, for cases indicated in.(a) and (b) above flows to the drains -in a direction approximately transverse to the direction of flow in canals and drains. The lines of flow from canal meet the drains at various dopes, depending upon the cross section of the drain. The problem can be simplified to the following two extreme conditions ( see Fig. 1 ). 3.4 Horizontal Drainage -- If the drain is shallow and wide, the stream lines of seepage flow from the canal may join the bottom of the drain at various points along its width as shown in Fig. 1A. In this case the bed of the drain represents an equip otential surface. 3.5 Vertical Drainage 3.5.1 If the drain is narrow, the seepage might enter it from both sides of the drain as shown in Fig. lB. In this case the streamlines of seepage flow from canals on both flanks of drain would reach the drain in a horizontal direction, and a vertical plane along the line of flow of the drain may be considered to represent an equip otential surface. Such a flow situation may also arise when seepage occurs from a canal to a shallow water table. Far away from the canals, in the zone of uniform flow of ground water, the streamlines would be almost horizontal and the equipotential lines nearly vertical. Such an equipotential line may be considered to represent a vertical drain, .5 IS :9447-1980 AL 1A Horizontal drainage IB Vertical drainage * FIG, 1 SEEPAGEFROMCANALSTO DRAINAGES 3.5.2 In practice the flow may not fall distinctly into either horizontal or vertical drainage but may be a combination of the two. In such cases a fair idea of the flow would be obtained by a study of the two extreme cases. 3.5.3 The solution of the problems is obtained by conformal mapping by transforming the physical plane on to rectangular flow field through intermediate fictitious planes. The derivations obtained are rather involved. However, the results are plotted in the form of curves which make it easy to obtain the seepage discharge and the phreatic surface for any canal. 4. COLLECTION OF DATA 4.1 In order to assess the seepage losses and the profile of water table on either side of the canal, following data shoul~ be collected: a) Bed width of canal; b) Water depth inside the canal at full supply; c) Side slope of the canal; d) Distance of the governing drainages on either sides of the canals; e) Dry season and rainy season water level of drains on either side; f) Coefficient of permeability of the subsoil: The value of coefficient of permeability would be determined in field by a suitable method such as pumping out test; and to Profile of the subsoil to find out if any effective impermeable layer exists and its depth. 6 IS : 9447 - 1980 depend upon the order of variations in its. values of above parameters. Where variation in the subsoil permeability, the drainage distance and the difference in the water levels of the canal and drain is large, the data should be collected at a spacing of 2 km. Otherwise it may be collected at every 5 to 10 km spacing. 5. ESTIMATION OF SEEPAGE LOSSES AND PHREATIC SURFACE 5.1 Canals Located in Medium Extending Up to Infinite Depth, With Shallow Water Table 5.1.1 The procedure, both for horizontal and vertical drainage condition is given below. 5.1.1.1 Horizontal drainage - Knowing the dimensions of the system in the physical plane, the two parameters l3 and y are determined as follows: a) The bed width B, the slope angle x u in radians, the~distance up to drainage L, the water depth inside the canal H and the difference in water levels of the canal and drainage h are recorded for the subject case ( Fig. 2 ). b) Figure 3A can be used to obtain values of transformation parameters of p and y. The use of figure requires the values of b/H, L/H and CL' where b and a' are bed width and side slope of the channel in an intermediate plane. To start with the initial values of b and a' may be taken as equal to p and a respectively and values of p and y obtained from Fig. 3A. The values of b/H and L/H are represented along ordinate and abcissa of the graph respectively, for values of a' equal to 0.15, 0.25 and 0.35. The scales corresponding to the value of 0~' are used for determining the values of p and y. c) Figure 4 presents graphically the relationship between a and a' and Fig. 5 presents the relationship between B and b. With-the known values of h/H, u, $ and y, the values of a' and b/H are obtained from Fig. 4 and 5 respectively. d) With these values of b/H and a', better approximation to p and y are determined from Fig. 3A and the process is repeated until difference/variation in the values of p and y from one trial to another is negligible. This condition is normally achieved within three trials. Seepage discharge : Knowing p and y, the seepage discharge per unit length of channel 4 in terms of kh is obtained from Fig. 6. Phreatic surface : Figures 3A and 7 can be used parametrically to obtain x an-d y coordinates of the phreatic surface, For an assumed value 4.2 The drainages at which the above information shall be collected shall 7 IS : 9447 - 1980 of variable t between zero and y, a ratio t/y is determined. With this value of t/y and known value of e/y the value of y/h is obtained from Fig. 7. For the same value of t and the known value of 13, the value of x/H can be obtained from Fig. 3A by replacing L by X and y by t in that figure. 5.1.1.2 Vertical drainage - The procedure with vertical drainage is similar. The difference is that Fig. 3B is used instead of Fig. 3A for determining p and-y, and x/h. The seepage discharge and phreatic surface profile are determined separately for either side of the canal. The total seepage is obtained by adding the seepage discharge estimated for either aide. 1 =--X h 2A Horizontal drainage = x h t _-l -L--m t Y E 28 Vertical drainage F I G. 2 P HYSICAL P L A N E 8 l/H IN T H O U S A N D S 3A Values of p and y horizontal drainage _ F I G. 3 VALUES OF p AND y DkAINAGEs- Con& w b n `"\\\\I \ I \ T b 0861- LPP6 : SI IS : 9447 - 198cD 0.15 0.20 2 1 0.30 L8 040 0.50 0.60 O?O -1 0.80 0 ----_ '8 tr u" FIG. 4 RE L A T I O N B ETWEEN a AND (x' E-3 : 9447 - 1980 (B-bl/H 8 6 2 0 B F I G. 5 RELATIONSVIP BE T W E E N B AND b lo-' 10-4 10-j P/-f F I G. 6 SEEPAGE D ISCHARGE qlkh 12 13~. 7 ORDINATES OF F REE SURFACE 5.2 Canals Located in Medium Extending Up to Finite Depth with Shallflow Water Table - Of the various methods in vogue, closed form method is generally adopted which is given below. 52.1 The procedure for determining the seepage discharge for the canal both for horizontal and vertical drainage conditions ( Fig. 8 ) is given below. 5.2.2 Seepage Discharge - Knowing the dimensions of the system in the physical plane, the two parameters IS and p are determined from Fig. 9 and 10 for horizontal and vertical drainage conditions respectively. Fig. 11 and 12 are used for determining non-dimensional seepage discharge qlkh for horizontal and vertical drainage conditions respectively. 5.2.3 Phreatic Swface .--- Figures 13 and 14 can be used parametrically to obtain x and y coordinates of the phreatic surface. For the known values of Q and CS/@ the coordinates of phreatic surface can be obtained from these figures. The phreatic surface have been plotted for o=lO-", IC-10, 10-20, IO-30 and CS/@ ranging-between 1O-2 and 102. 13 IS : 9447 - 1980 IMPERMEABLE LAYER 8A Horizontal drainage L IMPERMEABLf LAYER 88 Vertical drainage F I G. 8 P HYSICAL P LANES OF D RAINAGES 5.3 Canals Located in Medium Extending Up to Infinite Depth with Deep Water Table - The solution for this boundary condition was obtained by Vedernikov with the help of conformal mapping. The seepage discharge, q per unit length of channel is given by: q"1C[B+(A+2m)H] =k(B,$-`4H) where B = Bed width of channel ; B, = Surface width of channel; H = water depthinside channel; and A is function of geometry of canal,. The value of A is obtained from Fig. 15 for the known values of B/H or B,/H and m, where m = cot rt cc and x 01 = side slope angle. 14 10 10 10 1.0 10: 5 :: ," ij lo2 10 lo3 VALUE OF , lo2 t .UE O F II 10 /I I 6 1.0 V A L U E OF L/h FIG. 9 R E L A T I O N B E T W E E N L/h, T/h, G AND p ( HORIZONTAL D RAINAGE ) 15 IS : 9447 - 1980 1 I // i / I -~I _-. .0~001 _-- -.. odm ..' --~ --~--7 0 I I , 1 102 103 104 105 VALUE OF L/h -4 B f3 10 l71~. 10 RE L A T I O N B ETWEEN L/h, T/h, ( V ERTICAL D RAINAGE ) (r AND IS : 9447 - 1980 VALUE OF L/h FIG. 11 SEEPAGE DISCHARGE ( HORIZONTAL DRAINAGE ) 17 IS : 9441- 1980 14 WITHOUT CLAY WIT 3UT CLAY -.WITHOUT CLAY LAYER7 n 2 I IO5 VALUE OF t/h IO4 105 F I G. 12 S EEPAGE D I S C H A R G E ( VE R T I C A L D R A I N A G E ) 18 IS : 9447 * 1980 VALUE OF x/L F I G. 13 C OORDINATES OF P HREATIC S U R F A C E ( HORIZONTAL D RAINAGE ) 19 IS : 9447 - 1980 d) 6=10 0 0.2 aI.4 0.6 O-6 14,O O-2 1 -30 04 O-6 O-0 1.0 VALUE OF x /L F I G. 14 COORDINATES OF P HREATIC S U R F A C E ( VERTICAL D RAINAGE ) 20 IS : 9447 - 1980 4.4 4.0 3b6 A 3.2 2*0 2.4 2-o la6 0 5 10 15 OF 20 61" F I G. 15 V ALUE A 6. LIMITATIONS 6.1 The drainage conditions on either side of the canal are assumed to be symmetrical and in practice may be different. The seepage losses and phreatic surface for both the sides are determined separately assuming that the dividing line is vertical through the centre of the canal. 7. EXAMPLE 7.1 A worked out example for cases given in 3.2(a), 3.2(b) and 3.2(c) is given in Appendix A. APPENDIX ( Clause 7.1 ) A A WORRED OUT EXAMPLE FOR CASES GIVEN IN 3.2(a), 3.2(b) and 3.2(c) Following are the physical dimensions of a canal for which seepage discharge and free surface on either side are to be determined ( Fig. 16 ): B = 68.8 m a) Bed width H = 3.44 m b) Water depth 0.147 77 x c) Side slop angle 21 IS : 9447 - 1980 Right side of channel a) Drainage distance b) Difference in channel and drainage water level Left side of channel L-53QOm lz = 725 m L = 10 600 m h= 8*4m FSL O F C A N A L a) Drainage distance b) Difference in channel and drainage water level LEFT RIGHT # w a: c w z WL goSURFACE *oL I t 10 8 6 I 4 I 2 I Q L I 2 L DISTANCE IN km F I G. 16 CROSS S ECTION S HOWING PHREATIC SU R F A C E For the case corresponding to 3.2 (a) the seepage losses are worked out as follows: Horizontal Drainage: For values of CL, B/H, L/H equal to 0.147 77, 20.0 and 1 540 respectively for the right-hand side, Fig. 3A, 4 and 5 yield the values of p = 3.5 and y = 5.0 x 10.4. For these values of p and y, the non-dimensional seepage loss q/kh is obtained from Fig. 6 as 0.52. Similarly the values of p and y for the left-hand side are obtained as 3.7 and 2.3 x 10" respectively. The value of nondimensional seepage discharge q/kh from Fig. 6 is obtained as 0.47. Taking an average value of coefficient of permeability equal to 2.5 x lo5 m/s, the seepage losses work out equal to 0,094 ms/sec/km and 0.099 ma/s/km considering the right and left sides boundary condition respectively. The average value of seepage losses works out as 0.096 5 ma/s/km. 22 IS : 9447 - 1980 Vertical Drainage: For values of a, B/H, L/H equal to 0,147 77, 20.0 and 1540 respectively for the right-hand side, Fig. 3B, 4 and 5 yield the values of @ = 3.5 and y 5= 2 x 1Q4. For these values of p and y, the nondimensional seepage loss q/kh is obtained from Fig. 6 as 0.55. Similarly the values of fi and y for the left-hand side are obtained as 0.48. For average value of coefficient of permeability equal to 215 x 10-s m/s, the seepage losses work out equal to 0.099 ma/s/km and O*lOO ma/s/km respectively considering right and left sides boundary conditions respectively. The average value of seepage losses work out as 0.100 ms/s/km. For the case corresponding to 3.2(b) when the canal isassumed to be located in medium underlain by animpervious layer at a depth of 100 m, the non-dimensional seepage discharge q/kh as obtained from Fig. 11 is 0.055 and 0.019 0 respectively for the right and left sides respectively for horizontal drainage. Similarly the non-dimensional seepage discharges, q/kh for vertical drainage case from Fig. 12 is 0.06 and 0.02 respectively. The average seepage discharge works out as 0*0071 ma/s/km and 0.007 5 m3/ s/km for the horizontal and vertical drainage conditions respectively. It is seen ~that these values are less than those obtained with infinite depth of permeable stratum. For the case corresponding to 3.2(c) when canal is underlain by deep water table the seepage losses work out 2.37 ms/s/km which are very large in comparison to values obtained for the conditions corresponding to 3.2(a) and 3.2(b). 23 INDIAN ON STANDA'RDS CANAL AND CANAL LININGS IS : 3860-1966 Precast cement concrete slabs for canal linings 3872-1966 Code of practice for lining of canals with burnt clay tiles 3873-1978 Code of practice for laying in-situ cement concrete lining on canals (Jirst revision ) 4515-1967 Code of practice for boulder linings for canals 4558A968 Code of practice for under-drainage of lined canals 4701-1968 Code of practice for earthwork on canals 4745-1968 Code of practice for design of cross section of lined canals 4839 ( Part I )-1979 Code of practice for maintenance of canals : Part I Unlined canals (&St revision ) 4839 (apart II )-1979 Code of practice for maintenance of canals: Part II Lined canals (Jirst revision ) 4839 ( Part III )-1979 Code ofpractice for maintenance ofcanals : Part III Canal structures, drains, outlets, jungle clearance, plantation and regulation (Jirst revision ) 4969-1968 Method of test for determiningfl exural strength of precast cement concrete slabs for canal lining 5256-1969 Code of practice for sealing joints in concrete lining on canals 5331-1969 Guide for selection of type of lining for canals 5690-1969 Guide for laying combination lining for existing unlined canals 5968-1968 Guide for planning and layout of canal system for irrigation 6004-1971 Criteria for hydraulic design of sediment ejector for irrigation and power channels 6522-1972 Criteria for design of silt vanes for sediment control in offtaking canals 6936-1973 Criteria for location, selection and hydraulic design of canal escapes 7112-1973 Criteria for design of cross section for unlined canals in alluvial soil 7113-1973 Code of practice for soil-cement lining for canals 7114-1973 Criteria for hydraulic design of cross regulators for canals 7495-1974 Criteria for hydraulic design of silt selective head regulator for sediment control in offtaking canals 7871-1975 Criteria for hydraulic design of groyne walls ( curved wing ) for sediment distribution at offtake points in a canal 7873-1975 Code of practice for line concrete lining for canals 7880-1975 Criteria for hydraulic design of skimming platform for sediment control in offtaking canal 7986-1976 Code of practice for canal outlets 8835-1978 Guidelines for planning and design of surface drains 9097-1979 Guide for laying lining of canals with hot bitumen or bituminous felts